gistfile1.txt

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark;

my %h = map { $_ => $_ } 1 .. 10;

my %subs = (
	for   => sub {
		my @a;
		push @a, "$_ $h{$_}\n" for keys %h;
		return @a
	},
	while => sub {
		my @a;
		while (my ($k, $v) = each %h) { 
			push @a, "$k $v\n"
		};
		return @a;
	}
);

for my $sub (keys %subs) {
	print "$sub => ", $subs{$sub}->(), "\n";
}

for my $n (10, 100, 1_000, 10_000) {
	%h =  map { $_ => $_ } 1 .. $n;
	print "\nfor a hash with $n keys:\n";
	Benchmark::cmpthese -1, \%subs;
}